Process for improving cellulosic materials



Patented Aug. 27, 1929.

UNITED STATES LEON DE WOLF, OF LEBBEKE, BELGIUM.

PROCESS FOR IMPROVING CELLULOSIC MATERIALS.

No Drawing. Application filed November 9, 1925, Serial No. 68,021, and in Belgium May 25,

This invention relates to a process for improving cellulosic materials and more particularly textile fibres, by the action of mixtures of caustic alkalis and other reagents.

It is known that caustic alkali solutions scour and mercerize vegetable fibres, but this action is generally accompanied by a pro nounced browning. It is also known that the .addition to the alkali bath either of methyl or ethyl alcohol, or of soap or sult'oricinates, facilitates the penetration of the alkali into the fibre and increases the rapidity as well as the strength of its action.

According to the invention, results are obtained in one single operation which are better than those obtained by the several treatments indicated above, by subjecting the fibres or other cellulosic materials to the action of a bath composed of a mixture of caustic alkali and a phenol. By phenol are hereinto be understood the monovalent- I t1on also gives remarkable results when other or poly'valent phenols and their homologues (cresols etc.).

This fact seems at first view paradoxical, on account of the well known acid character of the phenols and the name carbolic acid commonly given to ordinary phenol C H OH. But the present, invention is based upon the discovery of the fact that by virtue of their double character as acid and alcohol, the phenols are capable of acting at the same time,

' in one and the same bath, as an alcohol which assists the action of the alkali and as an acid which correets'and completes it. This action, I have ascertained, is such that it is possible to treat raw cellulosic materials and in particular vegetable fibres so as successively to perform, with the use of a single bath, the preliminary operations, i. e. scouring, degumming and Stripping-which are necessary to separate the eellulosic substances from foreign matters, and the finishing operations i. e. lanifying, mercerizing or even gelatinizing, whereby the material is transformed into a finished product adapted to be manufactured.

This phenomenon may be explained in the following manner: It is probable that alkaline phenolatesare formed in the bath according to the invention, but these so-called salts are unstable in an aqueous solution and the anions separate easily from the cations by hydrolysis. Such a separation is generally increased by the presence of porous materials. Now cellulosic materials are very porous and it is observed that during the course of the treatment the action upon the material is both that of an acid and that of an alcohol, as if these two bodies were simultaneously and individually in the presence of each other in the alkaline solution, each one keeping its particular properties. While the caustic alkali acts'in the known manner the phenol acts both in its capacity as an alcohol which assists the action of the alkali and in its capacity as an acid which has the ell'ect, amongst others, .of destroying the brown coloration produced by the alkali, as soon as it tends to appear. It has even been observed that in .the treatment of certain fibres which on account of their nature are in a fairly high state of purity, it is possible to scour, mercerize, lanify or gelatinize the material and at the same time to bleach it in a single operation without the assistance of another bleaching agent.

The use of the bath according to the invenreagents are added to it the action of which may thus be improved.

Unexpected results are obtained for in-, stance, when an oxidizing agent is added to the bath of alkali and phenol. The use of a mixture in predetermined proportions of a caustic alkali and an oxidizing agent acting in an alkaline medium is known for the treat ment of bast fibres with a view to obtaining at the same time lanification and bleaching. But when an oxidizing alkali bath has added to it a phenol, it is observed that in addition to the complex action exerted relatively to the alkali as described above, the phenol has a special action upon the oxidizing agent, which not only enables agents acting in an acid, or in aneutral medium to be employed (for example permanganates) as well as those which only act in an alkaline medium, but also enables the operation to be extendedto fibres having no bast such as cotton and cellulosic materials in general, with a View to obtainingat the same time as a thorough bleaching, either the lanification or the mercerizing or even the gelatinization of the material.

The special action of the phenols with regard to the oxidizing agent is the following,

alkaline hypochlorites being considered by Way of example. By virtue of their relative acidity the phenols seem to free a certain quantity of hypochlorous acid from its combination with the metal. A certain number of molecules liberated are absorbed by the nearest fibre, the remainder being absorbed ,7

until the quantity of hypochlorous acid againliberated is sufficiently great for the cycle to be recommenced. There is thus produced a constant molecular movement tending to produce equilibrium, which is in conformity to the law of Guldberg and Wage. During this treatment, as also in the general cas (alkali phenol bath) described in the first p different reagents, penetrating more and more deepl into the material, act simultaneously an individually upon the latter-with an efficiency which has not been obtained heretofore, while decreasing the attack upon the cellulosic material itself.

In practice, the quantities of phenol to be employed in the alkali-phenol bath, and the quantities of the other chemical ingredients which may be added thereto, may vary considerably according to the action it is desired to obtain, the conditions of operation, the temperature of the bath, the nature of the ingredients which may be added and above all upon the nature of the material to be treated.

The duration of the treatment may also be varied. With pure cellulose -the action is almost instantaneous and is complete at the end of about 5 minutes. For fibres incompletely'prepared (i. e.'boiled fibres for example) it may take nearly 2 hours; For certain crude impure fibres half a day or more may be needed.

The action of the mixture is effective at all temperatures and inpractice the tem nature will be one which is in keeping with t e object in view. Thus, for example, the operation may be carried out without heat orat a. moderate temperature for mereenzing or lanifying and at a higher temperature for gelatinization. As mentioned above, the one or the other of these results may be obtained at the same time as bleaching when an oxidizing agent is added to the bath, but the treatment in the alkali-phenol bath may also .be preceded by a separate bleaching, or this ace, the

treatment may be applied in all cases where use would previously be made of acid or alkaline baths with a view to improving the cellulosic materials.

In producing the various results obtainable according to this invention the efliciency of the process is enhanced when the alkali present in the bath is in exce of the amount required for forming a phe olate with the phenoL. When the bath is intended or 'lanifying, mercerizing or gel'atinizing it is desirable that it should contain at least 5% of caustic alkali and at least 1% of phenol.

manner, the process according to the invention may be applied to the lamfication of jute in the following manner;

After having previously soaked the 'utefibres in a cold or hike-warm solution-o an oxidizing bath, they are rinsed, wrung carefully and subjected for 5 or 10 minutes to the action of a bath composed of one volume of caustic soda in an aqueous solution at 38 Baum and one volume of 33% phenol (carv substances'and to transform said materials.

into a finished product. 2. A process of improving vegetable textile fibres, consisting in immersing crude By way of example, and in a non-limiting fibres in a bath containing at least 5% of caustie alkali and at least 1% of phenol in solution for a time suflicient to separate said fibres from the accompanying foreign substances and then to transform said fibres into a finished roduct adapted to be manufactured.

3. 5 process of improving cellulosic materials, consisting in subjecting said materials in the crude state to the action of a bath containing caustic alkali, a phenol and a bleaching agent in solution, .to separat said materials from the accompanying foreign substances,

and at the same time to bleach them and transform them into a finished product ready for manufacturin In testimony w ereof Ihereunto aifix my signature. LEON DE WOLF. 

